Conventional pulse oximetry has significant limitations because it works on the assumption that there are only two species of hemoglobin present in arterial blood, oxygenated hemoglobin (O2Hb) and reduced hemoglobin (RHb). In reality, two other hemoglobin species -- carboxyhemoglobin (COHb) and methemoglobin (metHb), collectively termed dyshemoglobins -- are present at all times. These two species of hemoglobin are formed endogenously at very low levels, but their quantities can increase to dangerous levels when carbon monoxide is present in inspired air or as a reaction to certain drugs or chemicals in the environment. All pulse oximeters used in medicine today, representing over 1,000,000 units worldwide, read oxygenation levels that are too high when there are elevated levels of dyshemoglobins in the blood. The alternative to pulse oximetry is to analyze arterial blood with a laboratory CO-oximeter. This procedure involves several different health care workers, potentially exposes personnel to blood borne pathogens, takes minutes or even hours to get results, and provides only a single data point in time. All of this adds cost, increases risks to health care workers, and delays appropriate treatment. Previous attempts by various companies to develop a noninvasive method of CO-oximetry have not succeeded. The limiting factors have been the correct selection of optical emitter wavelengths, spectral bandwidth of the emitters, and troublesome power instabilities of the requisite laser light sources. Kestrel Labs is developing a new oximeter that can use laser light sources for accurate photoplethysmographic measurements. This makes possible the world's first noninvasive and continuous four-analyte Pulse CO-Oximeter. It will provide clinicians with a powerful new tool for patient diagnosis and care. Kestrel Labs is addressing a major deficiency in pulse oximetry technology by developing a new type of oximeter that can simultaneously measure the four primary species of hemoglobin, including those that indicate whether a patient is suffering from carbon monoxide or certain forms of chemical poisoning. The only currently available option is to draw an arterial blood sample, send it to the hospital's blood lab, test it on an expensive blood analyzer, and wait until results are returned to the physician responsible for the patient's care. Kestrel Labs'new Pulse CO-Oximeter will provide accurate, continuous, and noninvasive measurements of these hemoglobin species, thereby avoiding additional costs, risks to health care workers, and delays to appropriate treatment. .